The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory captions and links exemplifying features within the Earth system. The community is invited to contribute digital imagery, short captions and relevant links.

Great Circle Scenes

Because the Earth is a sphere (oblate spheroid), the shortest distance between any two points occurs along a great circle, not a straight line as one might imagine from looking at a flat map. A great circle is the intersection of a circle and a sphere with the same diameters and common centers. The Equator is then of course a great circle. So if you fly from Detroit, Michigan to Japan, the route is not west across the Pacific but northwest past Hudson Bay, across the Bering Sea (above left -- note the ice floes) and then southwest across eastern Siberia (above center and right -- over mountains and meandering rivers).

My flight left Detroit at approximately 3:30 p.m. local time (Central Daylight Time) on October 20, 2006. We were in daylight the entire trip until just before landing in Japan. The Sun was perhaps 20 degrees above the horizon for much of the flight.